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We have been using Aurora serverless databases in staging and production environments for a few months now, and find the CPU remains in the range 15-20% almost all the time. However in the past week the CPU utilisation has been growing, even during periods of zero load and is now at 38%. I'm worried this trend will continue further and begin to become an issue.

I saw the same trend in our Staging environment, but it only lasted 3 days and then returned to the usual level.

What could be driving this and how should I be debugging and resolving the root cause(s)?

Chart from AWS database monitoring

SHOW FULL PROCESSLIST

Returns only 6 rows.

Results from SHOW FULL PROCESSLIST

----- Update 4th Sept 2019 -----

In the end, I just continued to monitor it, and once it reached 50% it dropped back down. I guess it is a quirk of Aurora serverless? Would be great to hear from anyone else facing this issue as I hate not understanding things.

enter image description here

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  • Use SHOW FULL PROCESSLIST to see what is running. Use the "slowlog" to see what queries are taking a lot of time. Meanwhile, I see that the "drop" occurs about midnight every night -- when Amazon do backups (or whatever)? – Rick James Aug 8 '19 at 22:16
  • @RickJames I added the results of SHOW FULL PROCESSLIST to the question. – Phil192 Aug 12 '19 at 8:21
  • Try again, or use the slowlog. – Rick James Aug 12 '19 at 15:13
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What solved it for me was setting the min and max instance count higher than before (forcing aurora to scale up, for example from min 2 ACU to min 4 ACU), and after scaling restoring the scaling settings.

I used 'Force scaling the capacity to the specified values when the timeout is reached' and 'Apply immediately'.

It also solved another issue we had, the 'Serverless database capacity' indicated 4 ACU while it was actually 2 ACU (as seen in the picture)

we expect 45% cpu with 2 instances, not 80%

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